International
Tables for Crystallography Volume H Powder diffraction Edited by C. J. Gilmore, J. A. Kaduk and H. Schenk © International Union of Crystallography 2018 |
International Tables for Crystallography (2018). Vol. H, ch. 2.5, p. 121
Section 2.5.2.2.1. Detector position in the laboratory system^{a}Bruker AXS Inc., 5465 E. Cheryl Parkway, Madison, WI 53711, USA |
The position of a flat detector is defined by the sample-to-detector distance D and the detector swing angle α. D and α are referred to as the detector-space parameters. D is the perpendicular distance from the goniometer centre to the detection plane and α is a right-handed rotation angle about the Z_{L} axis. Detectors at different positions in the laboratory coordinates X_{L}, Y_{L}, Z_{L} are shown in Fig. 2.5.4. The centre of detector 1 is right on the positive side of the X_{L} axis (on-axis), α = 0. Both detectors 2 and 3 are rotated away from the X_{L} axis with negative swing angles (α_{2} < 0 and α_{3} < 0). The detection surface of a flat 2D detector can be considered as a plane, which intersects the diffraction cone to form a conic section. Depending on the swing angle α and the 2θ angle, the conic section can appear as a circle, an ellipse, a parabola or a hyperbola.